U.S. patent application number 09/928452 was filed with the patent office on 2002-04-04 for apparatus and method for controlling oil pressure of an automatic transmission.
This patent application is currently assigned to UNISIA JECS CORPORATION. Invention is credited to Horiguchi, Masanobu.
Application Number | 20020038580 09/928452 |
Document ID | / |
Family ID | 18736062 |
Filed Date | 2002-04-04 |
United States Patent
Application |
20020038580 |
Kind Code |
A1 |
Horiguchi, Masanobu |
April 4, 2002 |
Apparatus and method for controlling oil pressure of an automatic
transmission
Abstract
When a different speed change request occurs during
pre-charging, an indicated pressure is stepwise changed up to a
standby pressure for after pre-charge, and a processing in
accordance with the different speed change request is commenced
with the indicated pressure after the stepwise change, as an
initial pressure.
Inventors: |
Horiguchi, Masanobu;
(Atsugi-shi, JP) |
Correspondence
Address: |
SUGHRUE, MION, ZINN
MACPEAK & SEAS, PLLC
2100 Pennsylvania Avenue, NW
Washington
DC
20037-3213
US
|
Assignee: |
UNISIA JECS CORPORATION
|
Family ID: |
18736062 |
Appl. No.: |
09/928452 |
Filed: |
August 14, 2001 |
Current U.S.
Class: |
74/732.1 |
Current CPC
Class: |
Y10T 74/19158 20150115;
F16H 61/686 20130101; F16H 61/061 20130101; F16H 2200/2007
20130101; F16H 2306/24 20130101; F16H 3/66 20130101 |
Class at
Publication: |
74/732.1 |
International
Class: |
F16H 047/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 14, 2000 |
JP |
2000-245567 |
Claims
What is claimed:
1. An apparatus for controlling oil pressure of an automatic
transmission comprising: a valve for controlling oil pressure
supply to a friction engagement element constituting an automatic
transmission, and a controller for pre-charging oil to the friction
engagement element which is engaged based on a speed change
request, by controlling said valve, wherein said controller
commences a processing based on said different speed change request
after performing a processing to make an indicated pressure for
said friction engagement element being pre-charged approach an
actual pressure in said friction engagement element, when a
different speed change request occurs during a pre-charge.
2. An apparatus for controlling oil pressure of an automatic
transmission according to claim 1, wherein said controller forcibly
delays commencement of speed change processing based on said
different speed change request, to make said indicated pressure
approach the actual oil pressure, when a different speed change
request occurs during said pre-charge.
3. An apparatus for controlling oil pressure of an automatic
transmission according to claim 2, wherein said controller
commences a speed change processing based on said different speed
change request, after a predetermined delay time has elapsed from
completion of said pre-charge.
4. An apparatus for controlling oil pressure of an automatic
transmission according to claim 3, wherein said controller modifies
said predetermined time in accordance with input shaft torque of a
speed change mechanism.
5. An apparatus for controlling oil pressure of an automatic
transmission according to claim 1, wherein said controller stepwise
reduces the indicated pressure for the friction engagement element
being pre-charged down to a reference pressure, to thereby make
said indicated pressure approach an actual oil pressure, and
commences a speed change processing based on said different speed
change request, with said indicated pressure after stepwise change
as an initial pressure, when a different speed change request
occurs during said pre-charge.
6. An apparatus for controlling oil pressure of an automatic
transmission according to claim 5, wherein said controller stores
previously a standby pressure for after said pre-charge, as said
reference pressure.
7. An apparatus for controlling oil pressure of an automatic
transmission according to claim 5, wherein said controller
determines said reference pressure in accordance with the actual
oil pressure in said friction engagement element being
pre-charged.
8. An apparatus for controlling oil pressure of an automatic
transmission according to claim 7, wherein said controller
estimates the actual oil pressure in said friction engagement
element being pre-charged, based on a time from commencement of
said pre-charge until a point in time when the different speed
change request occurs.
9. An apparatus for controlling oil pressure of an automatic
transmission according to claim 7, wherein there is provided an oil
pressure switch which is switched when the actual oil pressure in
said friction engagement element becomes a threshold value, and
said controller estimates the actual oil pressure in said friction
engagement element being pre-charged based on; a time from said
pre-charge commencement until said oil pressure switch is switched,
a time from when said oil pressure switch is switched until a point
in time when the different speed change request occurs, and a
threshold value for oil pressure in said oil pressure switch.
10. An apparatus for controlling oil pressure of an automatic
transmission according to claim 7, wherein said controller sets the
actual oil pressure at a point in time when said different speed
change request occurs, as said reference pressure.
11. A method of controlling oil pressure of an automatic
transmission, comprising the steps of; pre-charging oil to a
friction engagement element which is engaged based on a speed
change request, judging occurrence of a different speed change
request during said pre-charging, making an indicated pressure for
said friction engagement element being pre-charged approach an
actual oil pressure in said friction engagement element when a
different speed change request occurs, and commencing a processing
based on said different speed change request after the processing
to make said indicated pressure approach the actual oil
pressure.
12. A method of controlling oil pressure of an automatic
transmission according to claim 11, wherein said step of making the
indicated pressure approach the actual oil pressure includes the
following step of; forcibly delaying commencement of speed change
processing based on a different speed change request when said
different speed change request occurs during said pre-charge.
13. A method of controlling oil pressure of an automatic
transmission according to claim 12, wherein said step of delaying
commencement of speed change processing includes the following
steps of; measuring an elapse of a predetermined delay time from
completion of said pre-charge, and commencing the speed change
processing based on said different speed change request after a
point in time when said delay time has elapsed.
14. A method of controlling oil pressure of an automatic
transmission according to claim 13, wherein said step of measuring
delay time includes the following steps of; detecting input shaft
torque of a speed change mechanism, and setting said delay time in
accordance with said input shaft torque.
15. A method of controlling oil pressure of an automatic
transmission according to claim 11, wherein said step of making the
indicated pressure approach the actual oil pressure includes the
following steps of; setting a reference pressure for an indicated
pressure for said friction engagement element being pre-charged,
and stepwise reducing the indicated pressure for the friction
engagement element being pre-charged down to said reference
pressure, when a different speed change request occurs during said
pre-charge.
16. A method of controlling oil pressure of an automatic
transmission according to claim 15, wherein said step of setting
said reference pressure includes the following steps of; storing
previously a standby pressure for after said pre-charge, and
setting said standby pressure as said reference pressure.
17. A method of controlling oil pressure of an automatic
transmission according to claim 15, wherein said step of setting
said reference pressure includes the following steps of; detecting
the actual oil pressure in said friction engagement element being
pre-charged, and determining said reference pressure in accordance
with said actual oil pressure.
18. A method of controlling oil pressure of an automatic
transmission according to claim 17, wherein said step of detecting
an actual oil pressure includes the following steps of; measuring a
time from commencement of said pre-charge until a point in time
when the different speed change request occurs, and estimating said
actual oil pressure based on said measured time.
19. A method of controlling oil pressure of an automatic
transmission according to claim 17, wherein said step of detecting
the actual oil pressure includes the following steps of; measuring
a time from said pre-charge commencement until ON/OFF switching of
an oil pressure switch which is switched when the actual oil
pressure in said friction engagement element becomes a threshold
value, measuring a time from ON/OFF switching of said oil pressure
switch until the different speed change request occurs, and
estimating the actual oil pressure in said friction engagement
element being pre-charged based on said measured time and said
threshold value for the oil pressure switch.
20. A method of controlling oil pressure of an automatic
transmission according to claim 17, wherein said step of
determining said reference pressure in accordance with the actual
oil pressure includes the following steps of; detecting the actual
oil pressure at a point in time when said different speed change
request occurs, and setting said actual oil pressure at the point
in time when said different speed change request occurs, as said
reference pressure.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an apparatus and a method
for controlling the supply of oil pressure to a friction engagement
element such as a clutch in an automatic transmission.
RELATED ART OF THE INVENTION
[0002] Heretofore, in an automatic transmission for a vehicle,
there is known a construction where, when engaging a friction
engagement element such as a clutch, a pre-charge which is a
process for quickly filling oil to the friction engagement element
in advance, is performed, to thereby raise the oil pressure of the
friction engagement element to that just before engagement (refer
to Japanese Unexamined Patent Publication No. 5-106722).
[0003] However, there may be a case where, while performing the
pre-charge based on a speed change request, a different speed
change request is made giving rise to a requirement to conversely
release the friction engagement element which was to be engaged by
performing the pre-charge.
[0004] Heretofore, if as described above a different speed change
request is made during pre-charging, an indicated pressure for the
pre-charging is gradually reduced.
[0005] However during pre-charging, since the actual oil pressure
is lower than the indicated pressure due to a oil pressure response
delay, even though the indicated pressure is gradually reduced from
the time when the different speed change request has occurred, the
condition where the actual oil pressure is lower than the indicated
pressure is maintained for a while.
[0006] In such a condition, the actual oil pressure continues to
change upward, and as a result, the friction engagement element not
to be engaged starts engagement, so that a speed change shock is
likely to occur.
[0007] Furthermore, there is a situation where a speed change
request occurs during pre-charging, requiring an even more rapid
engagement of the friction engagement element.
[0008] In this case, the indicated pressure is further increased in
a condition where the actual oil pressure is lower than the
indicated pressure. Hence, the actual oil pressure is increasingly
changed at a speed exceeding the rising speed of the indicated
pressure, and due to this abrupt increasing change of the oil
pressure, an engagement shock is likely to occur.
SUMMARY OF THE INVENTION
[0009] Accordingly, it is an object of the present invention to
provide an apparatus and a method for controlling oil pressure,
which can avoid the occurrence of a speed change shock when a
different speed change request is made during pre-charging.
[0010] In order to achieve the above object, the present invention
is constructed so that when a different speed change request is
made during pre-charging, a processing based on the different speed
change request is commenced after a processing has been performed
to make an indicated pressure for a friction engagement element
being pre-charged approach an actual pressure.
[0011] The other objects and features of this invention will become
understood from the following description with reference to the
accompanying drawings.
BRIEF EXPLANATION OF THE DRAWINGS
[0012] FIG. 1 is a system diagram showing an automatic
transmission.
[0013] FIG. 2 is a time chart showing a hydraulic control at the
time of speed change.
[0014] FIG. 3 is a configuration diagram showing details of an
automatic transmission.
[0015] FIG. 4 is a diagram showing correlations between
combinations of engagement conditions of friction engagement
elements and speed change steps.
[0016] FIG. 5 is a flow chart showing a first embodiment of a
control for when a different speed change request is made during
pre-charging.
[0017] FIG. 6 is a time chart showing characteristics of a
pre-charge control in the first embodiment.
[0018] FIG. 7 is a flow chart showing a second embodiment of the
control for when a different speed change request is made during
pre-charging.
[0019] FIG. 8 is a time chart showing characteristics of a
pre-charge control in the second embodiment.
[0020] FIG. 9 is a flow chart showing a third embodiment of the
control for when a different speed change request is made during
pre-charging.
[0021] FIG. 10 is a time chart showing characteristics of a
pre-charge control in the third embodiment.
[0022] FIG. 11 is a flow chart showing a fourth embodiment of the
control for when a different speed change request is made during
pre-charging.
[0023] FIG. 12 is a time chart showing characteristics of a
pre-charge control in the fourth embodiment.
[0024] FIG. 13 is a flow chart showing a fifth embodiment of the
control for when a different speed change request is made during
pre-charging.
[0025] FIG. 14 is a time chart showing characteristics of a
pre-charge control in the fifth embodiment
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] FIG. 1 shows an automatic transmission of a vehicle.
[0027] Output torque of an engine 1 mounted on a vehicle is
transmitted to drive wheels (not shown in the figure) via an output
shaft 2a of an automatic transmission 2.
[0028] Automatic transmission 2 is constructed so as to perform
speed change by controlling the supply of engagement oil pressure
to a friction engagement element such as various clutches and
brakes, by means of a solenoid valve unit 3.
[0029] According to this embodiment, without using a one-way
clutch, the engagement and release of two friction engagement
elements is controlled simultaneously with oil pressure to perform
the speed change.
[0030] More specifically, as shown in FIG. 2, the engagement oil
pressure for the friction engagement elements to be engaged is
gradually increased while gradually reducing the engagement oil
pressure for the friction engagement elements to be released,
thereby shifting torque from the release side friction engagement
element to the engage side friction engagement element.
[0031] Automatic transmission 2, as shown in FIG. 3, is configured
to be input with the engine output torque via a torque converter
T/C, and incorporates a front planetary gear system 83, and a rear
planetary gear system 84, and also incorporates, as the friction
engagement elements, a reverse clutch R/C, a high clutch H/C, a
band brake B/B, a low and reverse brake L & R/B and a forward
clutch FWD/C.
[0032] In FIG. 3, reference symbol 81 denotes an input shaft of the
transmission, reference symbol 82 denotes an output shaft of the
transmission, and Ne denotes the engine rotational speed, Nt
denotes the turbine rotational speed, and No denotes the output
shaft rotational speed.
[0033] In this construction, as shown in FIG. 4, speed change is
performed in accordance with combinations of engagement and release
of the reverse clutch R/C, the high clutch H/C, the band brake B/B,
the low and reverse brake L & R/B and the forward clutch
FWD/C.
[0034] For example, at the time of shifting up from 3-speed to
4-speed, release of the forward clutch FWD/C and engagement of the
band brake B/B are performed simultaneously.
[0035] The respective solenoid valves of solenoid valve unit 3 are
controlled by a control unit 4 incorporating a microcomputer
therein.
[0036] Here, in engagement control of a friction engagement element
such as a clutch, the construction is such that rapid filling of
oil (pre-charge) is performed so that a space between a clutch
plate and a piston is filled up beforehand.
[0037] That is to say, in the case of engaging a friction
engagement element such as a clutch, at first by outputting for a
predetermined period, a predetermined pre-charge pressure as an
indicated pressure for the friction engagement elements to be
engaged, the friction engagement elements are stroked without
effect until just before engagement, and the indicated pressure is
changed stepwise and maintained at a critical pressure (standby
pressure) for just before commencing engagement.
[0038] After this, the indicated pressure of the engagement side is
gradually increased from the critical pressure while matching the
timing to a release control, so that the friction engagement
element is engaged.
[0039] There is a case where a different speed change request
(hereunder referred to as a further speed change request) occurs
during the aforementioned pre-charge. Aspects of a hydraulic
control for the case where this further speed change request has
occurred will be explained in accordance with the flow chart of
FIG. 5.
[0040] In the flow chart of FIG. 5, in step S1, it is judged if the
pre-charge is being performed on the friction engagement
element.
[0041] If the pre-charge is being performed, control proceeds to
step S2 where it is judged if the further speed change request has
occurred.
[0042] This further speed change request is a speed change request
different from a speed change request which triggered a pre-charge
control.
[0043] For example, this further speed change request is a speed
change request which requires to modify the pre-charge control
rather than continuing with the pre-charge control up until then,
in the case where after commencement of the pre-charge in
accordance with an up-shift request, conversely a down-shift
request occurs, so that engagement of the friction engagement
element being pre-charged is cancelled, or in the case where the
engagement speed of the friction engagement element being
pre-charged is to be changed even faster.
[0044] If the further speed change request occurs during
pre-charging, control proceeds to step S3, and stands by until the
pre-charge control is terminated.
[0045] Furthermore, an input shaft torque of a speed change
mechanism is detected in step S4, and corresponding to this, a time
t is set in step S5. Then in step S6, it is judged if this time t
has elapsed from the termination of the pre-charge control.
[0046] Then, once the time t has elapsed, control proceeds to step
S7, where a speed change processing (control of the indicated oil
pressure) is commenced based on the further speed change
request.
[0047] The further speed change processing is a processing for a
gradual reduction of the indicated oil pressure in the case of
canceling the engagement of the friction engagement element being
pre-charged, while this is a processing for a gradual increase of
the indicated oil pressure in the case of a modification to the
sudden engagement.
[0048] In the aforementioned step S4, an engine output torque is
estimated for example from the load and the rotational speed of the
engine 1, and the engine output torque is then converted based on a
torque ratio of the torque converter, to obtain the input shaft
torque of the speed change mechanism.
[0049] Furthermore, in step S5, the aforementioned time t is set to
a longer time, the larger the input shaft torque.
[0050] According to the abovementioned construction, even if the
further speed change request occurs during pre-charging, the
commencement of speed change processing based on the further speed
change request is delayed until termination of the pre-charge
control, and until the time t has elapsed.
[0051] While delaying the commencement of speed change processing
based on the further speed change request as described above, as
shown in FIG. 6, an actual oil pressure overtakes the indicated
pressure, and then becomes stable at close to the indicated oil
pressure.
[0052] Consequently, the speed change processing (specified oil
pressure control) based on the further speed change request is
commenced in a condition where the actual oil pressure and the
indicated pressure approximately coincide.
[0053] As a result, in the speed change processing based on the
further speed change request, the actual oil pressure (engagement
condition of the friction engagement element) can be controlled in
agreement with the request, by controlling the indicated pressure,
so that the occurrence of a shock can be avoided.
[0054] The flow chart of FIG. 7 shows a second embodiment of the
hydraulic control for the case where the further speed change
request occurs during the pre-charge control.
[0055] In the flow chart of FIG. 7, when judged in step S11 that
the pre-charge is being performed on the friction engagement
element, control then proceeds to step S12, and when judged that
the further speed change request has occurred, control proceeds to
step S13.
[0056] In step S13, the indicated pressure is changed stepwise from
the indicated pressure during the pre-charge control (pre-charge
pressure) to a critical pressure equivalent to a standby pressure
of the engagement control (refer to FIG. 8).
[0057] In step S14, the speed change processing based on the
further speed change request is commenced, with the indicated
pressure equivalent to the aforementioned critical pressure, as an
initial pressure.
[0058] The pre-charge control is aimed at increasing the actual oil
pressure towards the critical pressure. The pre-charge and the
pre-charge pressure are determined so that the actual oil pressure
approximates critical pressure when the pre-charge control is
terminated, and the actual oil pressure is gradually increased
towards the critical pressure.
[0059] On the other hand, since in order to perform rapid filling
of oil, the pre-charge pressure is set to a value which greatly
exceeds the critical pressure, then during pre-charging a
difference between the actual oil pressure and the critical
pressure is small compared to a difference between the indicated
pressure (pre-charge pressure) and the actual oil pressure.
[0060] Consequently, when the further speed change request occurs
during the pre-charge control, the processing for stepwise reducing
the indicated pressure to the critical pressure, becomes the
processing to make the indicated pressure approach the actual oil
pressure.
[0061] If the speed change processing based on the further speed
change request is commenced once the indicated pressure has come
close to the actual oil pressure, then in the speed change
processing based on the further speed change request, the actual
oil pressure (engagement condition of the friction engagement
element) can be controlled in agreement with the request, by
controlling the indicated pressure, so that the occurrence of a
shock can be avoided.
[0062] Furthermore, the further speed change processing can be
commenced simultaneously with the occurrence of the further speed
change request. Hence control conditions corresponding to the
further speed change request can be quickly obtained.
[0063] In the above, the construction is such that the indicated
pressure is reduced stepwise to the critical pressure. However,
provided the construction is such that when the further speed
change request occurs, the indicated pressure is stepwise changed
to the actual oil pressure, any difference between the indicated
pressure and the actual oil pressure at commencement of the
processing based on the further speed change request, can be made
smaller.
[0064] The flow chart of FIG. 9 shows a third embodiment which
estimates the actual oil pressure during pre-charging, and in the
case where the further speed change request occurs during the
pre-charge control, changes stepwise the indicated pressure up to
the estimated actual oil pressure.
[0065] In the flow chart of FIG. 9, when judged in step S21 that
the pre-charge is performed on the friction engagement element,
control then proceeds to step S22, and when judged that the further
speed change request has occurred, control proceeds to step
S23.
[0066] In step S23, the actual oil pressure P at that time is
computed based on the following equation:
P=(critical pressure/pre-charge time).times.elapsed time from
pre-charge commencement
[0067] In the pre-charge control, the pre-charge and the pre-charge
pressure are determined so that the actual oil pressure
approximates the critical pressure when the pre-charge control is
completed.
[0068] Therefore, assuming that the rise speed of the actual oil
pressure during pre-charging is constant, the rise speed becomes
rise speed=critical pressure/pre-charge time, if the initial
pressure is zero.
[0069] Consequently, if this rise speed is multiplied by the
elapsed time from commencement of the pre-charge, the actual
pressure P at that time is estimated (refer to FIG. 10).
[0070] In step S24, the estimated pressure is stepwise changed from
the pre-charge pressure to the actual pressure computed in step
S23.
[0071] Then in step S25, the speed change processing based on the
further speed change request is commenced, with the indicated
pressure set close to the actual oil pressure by the processing of
step S24, as the initial pressure.
[0072] As described above, with the construction where the
indicated pressure is stepwise changed to the estimated actual
pressure, then compared to the case where the indicated pressure is
stepwise changed uniformly to the critical pressure, the difference
between the indicated pressure and the actual oil pressure can be
made smaller.
[0073] Incidentally, in the case where an oil pressure switch 51 is
provided which is switched ON and OFF depending on whether the oil
pressure in the friction engagement element is less than a
reference value or equal to or more than the reference value, the
estimation accuracy for the actual oil pressure can be increased by
using a signal from oil pressure switch 51.
[0074] The flow chart of FIG. 11 shows a fourth embodiment for
estimating the actual oil pressure using oil pressure switch
51.
[0075] In the flow chart of FIG. 11, when judged in step S31 that
the pre-charge is performed on the friction engagement element,
control proceeds to step S32 to judge whether or not oil pressure
switch 51 has been switched from OFF to ON.
[0076] Oil pressure switch 51 is turned ON when the actual oil
pressure reaches a reference pressure P1 (<critical pressure) or
above, and is turned OFF when the actual oil pressure is less than
the reference pressure P1.
[0077] In step S32, it is judged whether or not oil pressure switch
51 has been switched from OFF to ON.
[0078] When judged in step S32 that oil pressure switch 51 has been
switched from OFF to ON, control proceeds to step S33 where 1 is
set to a flag F (initial value=0).
[0079] Next, in step S34, an elapsed time from pre-charge
commencement until the point in time when switching of oil pressure
switch 51 from OFF to ON is detected, is stored as t1.
[0080] In step S35, it is judged whether or not the further speed
change request has occurred. If judged that the further speed
change request has occurred, control proceeds to step S36.
[0081] In step S36, it is judged whether or not 1 has been set to
the aforementioned flag F. When the flag F is 0, control proceeds
to step S37.
[0082] The condition where the flag F=0 is a condition where, from
commencement of pre-charge, the actual oil pressure has not risen
to the reference pressure P1 being the threshold pressure of oil
pressure switch 51.
[0083] Then, at this time, as with the aforementioned step S23, the
rise speed of the actual oil pressure is obtained, assuming that
the actual oil pressure shall rise to the critical pressure in the
pre-charge time. This rise speed is then multiplied by the elapsed
time from pre-charge commencement, to estimate the actual oil
pressure at that time.
[0084] On the other hand, if the flag F=1, then oil pressure switch
51 has been previously switched from OFF to ON. Therefore, control
proceeds to step S38 to estimate the actual oil pressure for when
the further speed change request occurred, using the timing of the
switching of oil pressure switch 51.
[0085] In step S38, the actual oil pressure P is computed according
to the following equation:
P=(P1/t1).times.time after switching of the hydraulic switch
51+P1.
[0086] In the above equation, as shown in FIG. 12, t1 is the time
from pre-charge commencement until oil pressure switch 51 is
switched. Therefore, P1/t1 is the rise speed of the actual oil
pressure for the case where it is assumed that the actual oil
pressure rises at a constant speed from pre-charge commencement up
to P1.
[0087] Then, if this rise speed is multiplied by the time from
after switching of oil pressure switch 51 until occurrence of the
further speed change request, this gives an oil pressure rise
amount for after switching of oil pressure switch 51, and if P1 is
added to the oil pressure rise amount, this gives an estimation of
the oil pressure at the point in time where the further speed
change request occurs.
[0088] Once the actual oil pressure has been estimated in step S37
or step S38, control proceeds step S39 where the indicated pressure
is stepwise changed to the estimated actual oil pressure, and in
step S40, the speed change processing based on the further speed
change request is commenced, with the indicated pressure after the
stepwise change as the initial pressure.
[0089] As described above, with the construction where the rise
speed of the actual oil pressure is computed from the timing for
when oil pressure switch 51 is switched, the actual oil pressure
can be estimated at the point in time when the further speed change
request occurs corresponding to fluctuations in the rise speed.
Therefore, compared to the third embodiment shown by the flow chart
of FIG. 9, the indicated pressure can be made closer to the actual
oil pressure.
[0090] In the above, the construction provided with oil pressure
switch 51 was shown. However, in the case where there is provided
an oil pressure switch 52 for detecting the actual oil pressure of
the friction engagement element, the construction may be such that
when the further speed change request occurs during pre-charging,
the further speed change processing is commenced after stepwise
changing the indicated oil pressure up to the actual oil pressure
detected by oil pressure switch 52.
[0091] A fifth embodiment of the above construction is explained in
accordance with the flow chart of FIG. 13.
[0092] In the flow chart of FIG. 13, when judged in step S41 that
the pre-charge is performed on the friction engagement element,
control then proceeds to step S42, and when judged that the further
speed change request has occurred, control proceeds to step
S43.
[0093] In step S43, the actual oil pressure detected by oil
pressure switch 52 provided in the friction engagement element
being pre-charged, is read in.
[0094] In step S44, the indicated pressure for the friction
engagement element being pre-charged is stepwise changed up to the
actual oil pressure read in step S43, and in step S45, the speed
change processing based on the further speed change request is
commenced, with the indicated pressure which has been matched to
the actual oil pressure in the processing of step S44, as the
initial pressure (refer to FIG. 14).
[0095] In the above, the construction is such that the indicated
pressure is stepwise changed to the estimated value or detected
value of the oil pressure. However the construction may be such
that the indicated pressure is stepwise changed to an oil pressure
for where a predetermined value is added to the estimated value or
detected value of the oil pressure.
[0096] The entire contents of Japanese Patent Application No.
2000-245567, filed Aug. 14, 2000 are incorporated herein by
reference.
* * * * *